Accurate Analysis of Anisotropic Carrier Mobility and Structure-property Relationships in Organic BOXD Crystalline Materials.

Shi-Ping Wang,Yu Wang,Hong-Xing Zhang,Fu-Quan Bai,Fu-Kit Sheong,Hai-Tao Wang,Fang-Yi Chen

doi:10.3389/fchem.2021.775747

Abstract

Charge mobility is an essential factor of organic crystalline materials. Although many investigators have made important progress, the exact relationship between the crystal structure and carrier mobility remains to be clarified. Fortunately, a series of bis-1,3,4-oxadiazole derivatives have been successfully prepared and reported. They have similar main molecular fragments but different crystal packing modes, which provide an ideal research objective for studying the effect of molecular packing on charge mobility in organic photoelectric conversion systems. In this work, the charge mobilities of these molecules are systematically evaluated from the perspective of first-principles calculation, and the effect of a molecular overlap on orbital overlap integral and final charge carrier mobility is fully discussed. It can be seen that the small intermolecular distance (less than 6 Å) is the decisive factor to achieve high electron mobility in π stacking, and better mobility can be obtained by increasing the hole migration distance appropriately. A larger dihedral angle of anisotropy is an important point limiting the charge mobility in the herringbone arrangement. It is hoped that the correlation results between the crystal structure and mobility can assist the experimental study and provide an effective way to improve the photoelectric conversion efficiency of the organic semiconductor devices and multiple basis for multiscale material system characterization and material information.

Highlights

Compared with inorganic materials, organic materials in our daily life have unique advantages in terms of price, ease of property, fine-tuning, and flexibility, etc
The BOXD-D crystal is full of π stacking arrangements, herringbone arrangement exist in the structure of other BOXD derivatives which cannot be defined by the slip distance
Based on multiple model and high-precision first-principles computational analysis of dense packing of organic molecules, we reveal the effects of crystal structures with π-packing and herringbone arrangement for anisotropic electron and hole mobility

Summary

Introduction

Organic materials in our daily life have unique advantages in terms of price, ease of property, fine-tuning, and flexibility, etc. There are enormous applications of organic crystals, such as OFET and OLET The relationship between the structure and charge mobility, especially the direction of mobility, becomes an important area of study. This is an urgent issue that is to be solved by theoretical calculations (Chen et al, 2014; Chen et al, 2016; Yang et al, 2016; Rehn et al, 2018; and Chen X. et al, 2019)

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